1. Field of the Invention
The present invention relates to mechanisms for hoisting or other wise lifting or moving objects a certain distance. In particular, the hoisting mechanism of the present invention is suitable for hoisting flags, awnings, canopies and the like and especially the canopy of an umbrella.
2. Discussion of Background and Material Information
Conventional umbrellas provided with large canopies, such as garden or beach umbrellas, employ equipment for hoisting the canopy which is usually fastened in a lower area of the support rod. In such cases, the devices used to hoist the umbrella typically include a flexible cable or rope attached at one end to a spool of a reel with another end of the cable attached to a runner slideable mounted on the support rod to which braces are attached at one end, with another end of the braces being pivotally attached to connections which are usually fixed along a middle portion of frame ribs which support the canopy when the umbrella is opened. More recently, it has been proposed to string the flexible cable or rope from the spool over an appropriate pulley-type device, preferably including a guide wheel, positioned above the runner in an upper section of the support rod, and then back to the runner. In operation, as the spool of the reel is rotated, the flexible cable or rope is wound on the spool and exerts a pulling action on the runner causing it to slide upwardly towards the crown of the umbrella until the braces have fully extended to force the frame ribs outwardly to stretch the canopy to a fully open condition.
Such mechanisms may also be used to hoist the canopy of large umbrellas where the support rod is divided into upper and lower shaft sections mounted for pivotable movement relative to each other around a joint, hinge or similar device suitable for this purpose. In this type of arrangement, the reel is continuously rotated after the umbrella canopy has been fully opened so as to exert a pulling force on the upper shaft section causing it to pivot about the joint to adjust the position of the canopy to a desired angle.
The prior art mechanisms used to accomplish hoisting and adjusting the position of the canopy to a desired angle, however, suffer from numerous shortcomings. For example, after the umbrella canopy has been completely opened, the reel continues to be rotated to pivot the upper section of the shaft to a desired angle. During this manipulation, the reel mechanism and shaft experience two different tension forces. Consequently, different torsional forces must be used when cranking the reel during the opening and adjusting of the umbrella canopy. The shortcomings and disadvantages of such prior art mechanisms include the fact that once the umbrella canopy is opened, it becomes considerably more difficult to exert the forces during the winding of the reel necessary to cause the upper section of the shaft to pivot to the desired angle. In addition, because of the extreme tension which is experienced by the rope as the upper section of the support rod is pivoted, there is an increased chance that the rope will break. Even if this does not occur, the rope tends to become dislodged from the guide wheel of the pulley-type arrangement around which it is strung as a result of the increased torsional forces to which the rope is subjected during the second stage of the procedure.
The present invention provides a solution to these problems with the provision of a novel and unique hoisting device which does not require a flexible cable or rope to accomplish hoisting the canopy and pivoting the upper section of the support rod. The improvement of the apparatus of the present invention is an arrangement of gears, drive wheels, a track and related elements whereby different torsional forces are effected during the manipulations of opening the umbrella canopy and adjusting the angle of the canopy of the umbrella, respectively. As further described in detail below, the hoisting mechanism may be designed so that additional tension experienced as the drive shaft continues to be rotated to cause desired pivoting of the upper section of the shaft to adjust the angle of the canopy after the mechanism has been manipulated so as to fully open the umbrella is minimized.